Read head having shaped read sensor-biasing layer junctions using partial milling and method of fabrication

ABSTRACT

A method is disclosed for fabricating a read head for a magnetic disk drive having a read head sensor and a hard bias layer, where the read head has a shaped junction between the read head sensor and the hard bias layer. The method includes providing a layered wafer stack to be shaped. A single- or multi-layered photoresist mask having no undercut is deposited upon the layered wafer stack to be shaped. The layered wafer stack is shaped by the output of a milling source, where the shaping includes partial milling to within a partial milling range to form a shaped junction. A hard bias layer is then deposited which is in contact with the shaped junction of the wafer stack. A read head and a magnetic hard disk drive having a read head layer stack which has been partially milled are also disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to fabrication of electroniccomponents, and more particularly, this invention relates to shaping ofthe junction between a hard biasing layer and the free layer of amagnetic read sensor of a hard disk drive.

2. Description of the Prior Art

In recent years there has been a constant drive to increase theperformance of hard disk drives by increasing the areal data storagedensity of the magnetic hard disk. This is done by reducing the writtendata track width, such that more tracks per inch can be written on thedisk. This naturally requires that the width of the read head be reducedso magnetic field interference from adjacent data tracks is not pickedup. Read sensors, of which one type is referred to as a “spin valve”,developed to read trackwidths smaller than 130 nm depends upon theability to ion mill the sensor to these very small dimensions, and toreliably lift-off the deposited layer materials.

One method used in the prior art for milling the read sensors is shownin FIG. 5 (Prior art). Preferably a single mill step at high incidenceangle (0 to 15 degrees from normal incidence, i.e., perpendicular to theplane of the surface being milled) is used in conjunction with a 2-layerphotoresist mask 40, having an upper layer 42 and a lower layer 44 toshape the read sensor 46. Commonly, the lower layer 44 of the 2-layerphotoresist mask 40 is of a narrower dimension than upper layer 42 andof the trackwidth W 48 to form an undercut 49.

However, the limits of this technique are being reached because withtrackwidths less than 130 nm, the width of the photoresist lower layer44 becomes too small to support the upper layer 42. In response,techniques are being developed to use a photoresist mask which has noundercut. A single layer of photoresist or a multilayer structure can beused with no undercut formed.

After the read sensor or spin valve is completed, layers are depositedon both sides of the sensor. These generally include a seed layer, astabilizing or hard bias layer and a layer of electrical leads. Thejunctions where these layers meet the layers of the spin valve sensorare very crucial to performance of the disk drive. For advanced spinvalve read sensors used in magnetic recording heads, the hard bias tospin valve junction shape is especially critical. Different sensordesigns and head designs call for various junction shapes. It is verydesirable to vary the junction profile, and thus to affect the sharpnessof the free layer edges, sharpness of the pinned layer edges, and thematerial on which the hard bias layers are grown, hence affecting deviceperformance.

Referring now to FIG. 6, the stack of layers, referred to generally as awafer stack 52, typically includes a first shield layer 54, a dielectricgap layer 56 and a first seed layer 58, upon which the remainder of thestack 60-68 is built. The milling or shaping process has typicallyinvolved cutting through the upper stack layers, completely through thefirst seed layer to reach the dielectric gap layer. It has beendiscovered that there are several disadvantages to this “completemilling” and many advantages to a “partial milling” operation in whichsome layers of sensor stack are left behind after the patterningoperation, retaining a thin layer of material which covers thedielectric layer. In particular, when using complete milling, the thindielectric layer underneath the sensor may become damaged by ionmilling. This decreases manufacturing yields since there is more yieldloss due to shorting between the sensor and the bottom shield. Secondly,the amount of material removed with complete milling is greater. Thereis thus more redeposited material that gets thrown against the sensorduring milling processes. This is expected to give less clean junctions,with higher junction resistance. Also, the total milling time isnaturally longer, and consequently, there is more chance of ESD damage.

Another disadvantage of complete milling is that at the end of themilling process, there are typically islands of patterned material leftbehind, rather than a continuous film of material on the wafer at alltimes, as there is with partial milling. Thus, there is more chance ofcharge buildup and potential ESD damage with complete milling.

Additionally, with partial milling, it is possible to stop at differentpoints of the sensor stack (e.g. pinned layer), and achieve junctions ofdifferent shapes. Depending on the sensor film characteristics and hardbias/leads characteristics, this is expected to produce different sensorperformance based on junction shape.

Also, it is an advantage that only a thin seed layer for the hard biasis required in the partial mill case. In contrast for the complete mill,a thick seed layer may be required in order to align the hard bias withthe free layer. When depositing this thick layer, the amount of materialdeposited on the junction is significant. This can potentially increasejunction resistance, and also leads to a larger spacing between the hardbias layer and the sensor, which is undesirable.

Thus, there is a need for shaped junctions and a method for achievingsuch junction shapes in spin valve sensors where the junction isachieved by partially milling through the sensor stack.

SUMMARY OF THE INVENTION

The present invention includes a method for fabricating a read head fora magnetic disk drive having a read head sensor and a hard bias layer,where the read head has a shaped junction between the read head sensorand the hard bias layer. The method includes providing a layered waferstack to be shaped, where the layered wafer stack includes a first seedlayer. A single- or multi-layered photoresist mask having no undercut isdeposited upon the layered wafer stack to be shaped. A milling source isprovided which produces an output at a defined angle of projection, andthe angle of said layered wafer stack to be shaped is adjusted relativeto the angle of projection of the milling source. The layered waferstack is shaped by the output of the milling source, where the shapingincludes partial milling to within a partial milling range to form ashaped junction. The partial milling range preferably extends from belowthe free layer to a partial milling depth having a depth endpoint whichlies within said first seed layer. A hard bias layer is then depositedwhich is in contact with the shaped junction of the wafer stack.

A read head produced by this process, and a hard disk drive having aread head produced by this process are also disclosed.

It is an advantage of the present invention that the thin dielectriclayer underneath the sensor does not get damaged by ion milling.

It is another advantage of the present invention that manufacturingyields are improved since there are less yield losses due to shortingbetween the sensor and the bottom shield.

It is yet another advantage of the present invention that the amount ofmaterial removed is less, and therefore there is less redepositedmaterial that gets thrown against the sensor, thus producing cleanerjunctions, with potentially lower junction resistance.

It is a further advantage of the present invention that the total milltime is shorter, and thus there is less chance of ElectrostaticDischarge (ESD) damage.

It is a yet further advantage of the present invention that since themetal is not completely removed during a partial mill, islands ofmaterial are not left behind (unlike in the full mill case, where at theend of the milling process, there are islands of patterned material):rather, there is a continuous film of material on the wafer at alltimes, and thus there is less chance of charge buildup and potential ESDdamage.

It is still another advantage of the present invention that it ispossible to stop at different points of the sensor stack (e.g. pinnedlayer), and achieve junctions of different shapes. Depending on thesensor film characteristics and hard bias/leads characteristics, thisallows different sensor performance based on junction shape.

It is an additional advantage of the present invention that only a thinseed layer is required for the hard bias where partial milling isperformed. In contrast, where full milling is performed, a thick seedlayer maybe required in order to align the hard bias with the freelayer. When depositing this thick layer, the amount of materialdeposited on the junction is significant, which could potentiallyincrease junction resistance, and also leads to a larger spacing betweenthe hard bias layer and the sensor, which is undesirable.

These and other features and advantages of the present invention will nodoubt become apparent to those skilled in the art upon reading thefollowing detailed description which makes reference to the severalfigures of the drawing.

IN THE DRAWINGS

The following drawings are not made to scale as an actual device, andare provided for illustration of the invention described herein.

FIG. 1 shows a top plan view of an exemplary disk drive;

FIG. 2 illustrates a perspective view of view of an exemplary slider andsuspension;

FIG. 3 shows a top plan view of an exemplary read/write head;

FIG. 4 is a cross-section view of an exemplary read/write head;

FIG. 5 is a front plan view of the structure of a CIP read sensor of theprior art as seen from the ABS;

FIG. 6 is a front plan view of the structure of a CIP read sensor havingcomplete milling as seen from the ABS;

FIGS. 7-12 are front plan views of stages in the construction of a CIPread sensor having partial milling of the present invention as seen fromthe ABS; and

FIGS. 13-15 are front plan views of alternate embodiments of thestructure of a CIP read sensor having partial milling of the presentinvention as seen from the ABS.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a disk drive read head having partial millingof the sensor layers above the dielectric layer, and a method forproducing this read head.

A hard disk drive 2 is shown generally in FIG. 1, having one or moremagnetic data storage disks 4, with data tracks 6 which are written andread by a data read/write device 8. The data read/write device 8includes an actuator arm 10, and a suspension 12 which supports one ormore magnetic heads 14 included in one or more sliders 16.

FIG. 2 shows a slider 16 in more detail being supported by suspension12. The magnetic head 14 is shown in dashed lines, and in more detail inFIGS. 3 and 4. The magnetic head 14 includes a coil 18 and P1 pole,which also acts as S2 shield, thus making P1/S2 20. P1 S2 may also bemade as two discrete layers. The second pole P2 22 is separated fromP1/S2 by write gap 23.

The read sensor 50 is sandwiched between the first shield S1 30 and thesecond shield P1/S2 20. There is generally included an insulation layer32 between the rest of the length of S1 30 and P1/S2 20. The magnetichead 14 flies on an air cushion between the surface of the disk 4 andthe air bearing surface (ABS) 24 of the slider 16. The write headportion 26 and the read head portion 28 are generally shown, with theread head sensor 50 and the ABS 24.

There are two configurations of read head in common use in the industrytoday. These are called Current Perpendicular to the Plane (CPP), andCurrent In the Plane (CIP). In the CPP configuration, Shield S1 andP1/S2 are made of conducting material which act as electrodes supplyingcurrent to the read sensor which lies between them.

The present invention uses a CIP configuration, in which the currentflows from side to side through the elements. For CIP read heads, theread sensor 50 is generally sandwiched between two insulation layers,usually designated G1 34 and G2 36 which are made of non-conductivematerial, to keep the circuit from shorting out. For the purposes ofthis discussion, the read head will be considered to be in CIPconfiguration.

The wafer stack 52 which will be shaped into a CIP (Current In thePlane) read head sensor 50 of the present invention is constructed asshown in FIG. 7, which is a front plan view as seen from the Air BearingSurface (ABS). The layers of a CIP read head are generally the same asshown in FIG. 7, and a side cross-section view of a finished read headwould look very much like FIG. 7. However, FIG. 7 will be assumed to bea view of a wafer stack 52 as seen from the Air Bearing Surface (ABS)before it is shaped into a read head. The stack includes a firstmagnetic shield 54, corresponding to S1 in the previous discussion,typically of NiFe, fabricated on a substrate (not shown). A dielectricgap layer 56 is formed on the magnetic shield 54. A first seed layer 58is deposited upon the dielectric gap layer 56. Further layers are formedon top of the layers below, typically in the order of anantiferromagnetic layer 60, a pinned layer 62, a spacer layer 64, a freemagnetic layer 66, and a cap layer 68. The spacer layer 64 may includeCu, Ru, etc. and the free layer 66 may include CoFe, NiFe, Co, etc. Thecap layer 68 may include Ta.

Note that this structure is strictly for illustration only, and oneskilled in the art will appreciate that sensor structures can varydramatically from the one shown in FIG. 7, the methodology of thepresent invention being applicable to formation of all such heads.

As shown in FIG. 8, a layer of masking material 70 is applied to thewafer stack 52. Note that the layer 70 may be formed of a single layer,a bi-layer, a tri-layer, etc. of one or more materials. This maskingmaterial protects underlying material from removal by such processes asion milling, and can thus be used as a shield or stencil to pattern theunderlying material. This masking material consists of a top layer ofphotoresist or other polymer that can be patterned usingphotolithography techniques. Suitable resists include i-line, deep UV,and e-beam sensitive resists. The underlying layers (if used) can bepolymethylglutarimide (PMGI) available from MicroChem Corp., Duramide,diamond like carbon (DLC), etc. If an underlying material is used, thiswould be patterned by chemical dissolution or reactive ion etchingthrough the photoresist mask.

Material is removed from the layer of photoresist 70, as shown in FIG.9, to form a mask layer 72. Any suitable process, such asphotolithograpy or reactive ion etching (RIE), can be used to removeportions of the photoresist 70, to shape it into the mask layer 72. Itshould be noted that the structure of the mask layer 72 does not have anundercut as discussed above in relation to the prior art, meaning thatthe width of the mask layer 72 after patterning is substantiallyconstant from top to bottom.

As shown in FIG. 10, the mask layer 72 is used as a mask for ionmilling/reactive ion beam etching or sputter etching to remove materialof the wafer stack 52 at the exposed areas around the mask layer 72 thusforming a shaped wafer stack 74. To obtain a profile of the shaped waferstack 74 which is relatively vertical, milling is performed at highincidence, i.e., about 0-25 degrees from normal incidence, preferablyabout 0-15 degrees from normal incidence, or from another perspective,about 65-90 degrees, preferably about 75-90 degrees from the surfacebeing milled as indicated by direction arrow 1. However, this commonlycauses redeposition of material on the sides of the shaped wafer stack74. To remove redeposited material, the shaped wafer stack 74 is milledat razing incidence, i.e., about 60-90 degrees from normal incidence,preferably about 60-85 degrees from normal incidence, as shown by seconddirection arrow 3.

These angles provide a milling rate that reduces the top of the waferstack 52 faster than the side of the wafer stack 52. This is becausewhen the top is milled at less than about 25 degrees from normalincidence, a small amount of the milling affects the sides. At razingincidence, both the top and sides of the wafer stack 52 are milled, withmore milling at the sides of the wafer stack 52.

Ideally, alternating milling cycles are performed at normal and razingincidence, or with the milling angle being pivoted between normal andrazing incidence. Optionally, milling can be performed at additionalangles between normal and razing incidence. Many alternating cycles arepreferred, because redeposited material may build up to create aprotrusion that causes shadowing.

The shaped wafer stack 74 after all milling has been completed is shownin FIG. 11. It should be noted that in this case, the milling has cutthough the upper layers through the AFM 60 layer and partially into thefirst seedlayer 58, but stops before it reaches the dielectric layer 56.Partial milling can be controlled by many different methods, includingsecondary ion mass spectroscopy, optical emission end-point monitoring,and also other well-known techniques such as use of a stop layer can beused.

There are several reasons and advantages for using this “partialmilling” of the first seed layer 58. First, using partial milling, thethin dielectric layer underneath the sensor does not get damaged by ionmilling. This improves manufacturing yields since there is less yieldloss due to shorting between the sensor and the bottom shield. Secondly,the amount of material removed is less. There is thus less redepositedmaterial that gets thrown against the sensor during mill processes. Thisis expected to give cleaner junctions, with lower junction resistance.Also, the total milling time is naturally shorter, and consequently,there is less chance of ESD damage.

Another advantage is that since metal is not completely removed during apartial mill, islands of material are not left behind (unlike in thefull mill case, where at the end of the milling process, there areislands of patterned material). Rather, there is a continuous film ofmaterial on the wafer at all times. Thus, there is less chance of chargebuildup and potential ESD damage.

Additionally, it is possible to stop at different points of the sensorstack (e.g. pinned layer), and achieve junctions of different shapes.Depending on the sensor film characteristics and hard bias/leadscharacteristics, this is expected to produce different sensorperformance based on junction shape.

Also, it is an advantage that only a thin seed layer for the hard biasis required in the partial mill case. In contrast for the full mill, athick seed layer may be required in order to align the hard bias withthe free layer. When depositing this thick layer, the amount of materialdeposited on the junction is significant. This can potentially increasejunction resistance, and also leads to a larger spacing between the hardbias layer and the sensor, which is undesirable.

For all these reasons, partial milling is done into or to a point priorto the first seed layer 58 to produce the structure seen in FIG. 11.

It should be noted that while it is necessary that the free magneticlayer 66 be completely etched, shaping of the other layers between thefree layer 66 and the first seed layer 58, is dictated by the junctionshape that is desired. More specifically, these layers include thespacer layer 64, the pinned layer 62 and the AFM layer 60. Thus, theterm “partial milling” as used for purposes of this application willinclude milling processes that extend at least through the free magneticlayer 66, but stop short of milling completely through the first seedlayer 58.

For this reason, the partial milling operation will be defined to extendwithin a range designated as the partial milling range 61. One exampleis having a partial milling depth endpoint 63, which is located withinthe first seed layer 58, but not extending through to the dielectriclayer 56, as seen in FIG. 11. Another example of a partial milling depth65 within this partial milling range 61 and extending to a depthendpoint 67 is shown in dashed lines also in FIG. 1. This corresponds toa partial milling operation which extends into, but not through, the AFMlayer 60. In such a case, the first seed layer 58 will not be reachedand its upper surface will continue to form a flat stratum as indicatedby dashed line 69.

As shown in FIG. 12, next a seedlayer 80 of a suitable material such asCr, etc. is deposited. A hard bias layer 82 is then added which mayinclude CoPt, CoPtCr, etc., forming a crucial junction 86 with theshaped stack layers 74, especially being in close proximity to the freelayer 66. The hard bias layer 82 is used to keep the domains in the freelayer 66 in a default alignment so they are not allowed to alignrandomly. This hard biasing improves magnetic stability and hence thesignal to noise performance. A layer of electrical leads 84 is thenadded upon the hard bias layer 82 using any suitable process, such assputter deposition.

The photoresist mask 72 stays on after the milling is done, until thehard bias layer 82 and lead layer 84 has been deposited. Then the mask72 is removed, and in the process, the hard bias and lead layer materialthat gets deposited on top of the mask 72 gets removed (or “liftedoff”).

Thus, a lift off process is used to remove the photomask 72, leaving theshaped wafer stack 74 shown in FIG. 13.

Additional layers may then be added to the shaped wafer stack 74, suchas upper layers of dielectric material (not shown) and a second shieldlayer (not shown).

Also, optionally, a layer of diamond-like carbon (not shown) can beadded if subsequent processing includes Chemical Mechanical Polishing(CMP). The diamond-like carbon will protect the new-formed sensor 50from damage during the CMP.

A sharp junction shape can be achieved by ion milling at an angle of0˜15°, as shown in FIG. 13. Ion milling at a shallower angle would givea more sloped junction shape, as shown in FIG. 14. Ion milling at asharp angle (0˜15°) followed by a shallow angle (60˜85°) can give asharper junction, as depicted in FIG. 15. Thus FIGS. 14 and 15 showvariations injunction shapes 86 caused by varying the angle of millingso that the side angles of the shaped wafer stack 74 have differentslopes. The angles have been exaggerated and are not to be interpretedas limitations on the actual angles achieved. The varying shapes of thejunction angles 86 are expected to produce various results in theperformance of the read sensor, such as read track width, signalamplitude, magnetic stability, noise performance and signal to noiseratio. However, all of these various junction shapes are expected toexhibit the advantages discussed above in regards to the partial millingof the sensor stack.

While the present invention has been shown and described with regard tocertain preferred embodiments, it is to be understood that modificationsin form and detail will no doubt be developed by those skilled in theart upon reviewing this disclosure. It is therefore intended that thefollowing claims cover all such alterations and modifications thatnevertheless include the true spirit and scope of the inventive featuresof the present invention.

1. A method for fabricating a read head for a hard disk drive having aread head sensor and a hard bias layer, said read head having a shapedjunction between said read head sensor and said hard bias layer, saidmethod comprising: A) providing a layered wafer stack to be shaped, saidlayered wafer stack including a free layer, an AFM layer and a firstseed layer; B) depositing a single- or multi-layered photoresist maskhaving no undercut upon said layered wafer stack to be shaped; C)providing a milling source which produces an output at a defined angleof projection; D) adjusting the angle of said layered wafer stack to beshaped relative to said angle of projection of said milling source; E)partially milling said layered wafer stack by said output of saidmilling source to within a partial milling range which extends to apartial milling depth having a depth endpoint, to form a shapedjunction: and F) depositing said hard bias layer in contact with saidshaped junction.
 2. The method of shaping of claim 1, wherein: saidpartial milling range extends from below said free layer to a partialmilling depth having a depth endpoint which lies within said first seedlayer.
 3. The method of shaping of claim 2, wherein: said partialmilling depth lies within said partial milling range and where the depthendpoint lies within said AFM layer.
 4. The method of shaping of claim1, wherein: the milling source is ion milling or reactive ion beametching.
 5. The method of shaping of claim 1, wherein: said millingsource is angled relative to said layer structure to be shaped.
 6. Themethod of shaping of claim 1, wherein: said layer structure to be shapedis angled relative to said milling source.
 7. The method of fabricationof claim 1, wherein: D) includes adjusting said angle at high incidence.8. The method of fabrication of claim 7, wherein: D) includes adjustingsaid angle at razing incidence.
 9. The method of fabrication of claim 8,wherein: E) includes multiple cycles of milling at both high incidenceand razing incidence.
 10. A method for fabricating the read head of amagnetic disk drive, the method comprising: A) depositing a first shieldlayer to begin a wafer stack; B) depositing a dielectric layer on saidfirst shield layer; C) depositing a first seed layer on said dielectriclayer; D) depositing an AFM layer on said first seed layer; E)depositing at least one pinned layer on said AFM layer; F) depositing aspacer layer on said at least one pinned layer; G) depositing a freelayer on said spacer layer; H) depositing a cap layer on said free layerto complete said wafer stack; I) depositing a mask layer on said caplayer to mask a portion of said wafer stack; and J) partially millingsaid wafer stack with a milling source to remove material from waferstack layers to within a partial milling range which extends to apartial milling depth having a depth endpoint, to form a shapedjunction.
 11. The method of fabrication of claim 10, wherein: J)includes milling at high incidence.
 12. The method of fabrication ofclaim 11, wherein: J) further includes milling at razing incidence. 13.The method of fabrication of claim 12, wherein: J) includes multiplecycles of milling at both high incidence and razing incidence.
 14. Themethod of fabrication of claim 10, further comprising: K) depositing asecond seed layer.
 15. The method of fabrication of claim 14, furthercomprising: L) depositing a hard bias layer.
 16. The method offabrication of claim 15, further comprising: M) lifting off said masklayer.
 17. The method of fabrication of claim 16, further comprising: N)depositing a leads layer.
 18. The method of fabrication of claim 15,wherein: J) includes shaping portions of said wafer stack so that thejunction between said portions of said wafer stack and said hard biaslayer is shaped.
 19. The method of fabrication of claim 13, wherein:said mask layer of I has no undercut.
 20. The method of fabrication ofclaim 10, wherein: said partial milling range extends from below saidfree layer to a partial milling depth having a depth endpoint which lieswithin said first seed layer.
 21. The method of fabrication of claim 20,wherein: said partial milling depth lies within said partial millingrange and where the depth endpoint lies within said AFM layer.
 22. Aread head for a hard disk drive, produced by the process comprising: A)depositing a first shield layer to begin a wafer stack; B) depositing adielectric layer on said first shield layer; C) depositing a first seedlayer on said dielectric layer; D) depositing an AFM layer on said firstseed layer; E) depositing at least one pinned layer on said AFM layer;F) depositing a spacer layer on said at least one pinned layer; G)depositing a free layer on said spacer layer; H) depositing a cap layeron said free layer to complete said wafer stack; I) depositing a masklayer on said cap layer; and J) partially milling said wafer stack witha milling source to remove material from wafer stack layers to within apartial milling range which extends to a partial milling depth having adepth endpoint, to form a shaped junction.
 23. The read head of claim22, wherein: J) includes milling at high incidence.
 24. The read head ofclaim 23, wherein: J) further includes milling at razing incidence. 25.The read head of claim 24, wherein: J) includes multiple cycles ofmilling at both high incidence and razing incidence.
 26. The read headof claim 25, further comprising: K) depositing a second seed layer. 27.The read head of claim 26, further comprising: L) depositing a hard biaslayer.
 28. The read head of claim 27, further comprising: M) depositinga leads layer.
 29. The read head of claim 28, further comprising: N)lifting off said mask layer.
 30. The read head of claim 27, wherein: J)includes shaping portions of said wafer stack so that the junctionbetween said portions of said wafer stack and said hard bias layer isshaped.
 31. A magnetic hard drive comprising: a read sensor having acentrally disposed wafer stack including: a first shield layer; adielectric layer on said first shield layer; a first seed layer on saiddielectric layer; an AFM layer on said first seed layer; at least onepinned layer on said AFM layer; a spacer layer on said at least onepinned layer; a free layer on said spacer layer; and a cap layer on saidfree layer; and at least one laterally disposed second seed layer; atleast one laterally disposed hard bias layer; and at least one laterallydisposed electronic leads layer; wherein said wafer stack has beenshaped with a milling source to remove material from wafer stack layersto within a partial milling range which extends to a partial millingdepth having a depth endpoint, to form a shaped junction.
 32. Themagnetic hard drive of claim 31, wherein: said shaped wafer stackincludes shaped junctions between portions of said free layer andportions of said at least one hard bias layer.
 33. The magnetic harddrive of claim 31, wherein: said partial milling range extends frombelow said free layer to a partial milling depth having a depth endpointwhich lies within said first seed layer.
 34. The magnetic hard drive ofclaim 33, wherein: said partial milling depth lies within said partialmilling range and where the depth endpoint lies within said AFM layer.